1. Field of the Invention
The present invention relates to a pellicle. More particularly, the present invention relates to a lithographic pellicle suitably used as a debris shield in the production of a semiconductor device such as an LSI or a ULSI, and to a lithographic pellicle particularly suitably used for UV irradiation of 200 nm or below which is employed in exposures where high resolution is required.
2. Description of the Related Art
Conventionally, in the production of a semiconductor device such as an LSI or a VLSI, or the production of a liquid crystal display panel, a pattern is formed by irradiating a semiconductor wafer or a liquid crystal substrate with light; if debris is attached to the exposure master plate used here, since the debris absorbs the light or reflects the light, there are the problems that the replicated pattern is deformed, or the edge becomes rough, or thus impairing the dimensions, quality, appearance, etc., resulting in the decrease in the performance and the manufacturing yield of semiconductor devices or liquid crystal display panels.
For this reason, these operations are usually carried out in a clean room, but always keeping an exposure master plate clean even within a clean room is difficult, and hence there is employed a method in which a pellicle that allows exposure light to easily pass through is affixed to the surface of the exposure master plate to act as a debris shield.
In this case, the advantage is that the debris does not attach directly to the surface of the exposure master plate but becomes adhered to the pellicle film, so that during lithography, the debris on the pellicle film does not become involved in the replication provided that the focus is set onto the pattern of the exposure master plate.
The pellicle has a constitution in which a transparent pellicle film made of nitrocellulose, cellulose acetate or etc., which allows exposure light to easily pass through, is adhered on the upper part of a pellicle frame made of aluminum, stainless steel, polyethylene or etc., by coating the upper part of the pellicle frame with a good solvent for the pellicle film and then air-drying the solvent (ref. JP-A-58-219023; JP-A denotes a Japanese unexamined patent application publication) or by means of an adhesive such as an acrylic resin, an epoxy resin or etc. (ref. U.S. Pat. No. 4,861,402, JP-B-63-27707 and JP-A-7-168345; JP-B denotes a Japanese examined patent application publication), while on the under part of the pellicle frame is attached a pressure-sensitive adhesive layer comprising a polybutene resin, a polyvinyl acetate resin, an acrylic resin, a silicone resin or etc., and a release layer (separator) for protection of the pressure-sensitive adhesive layer.
In recent years, lithography resolutions have been gradually increasing, and therefore the employed light sources are slowly shifting to shorter wavelengths to realize such resolutions. Specifically, there is a shift towards g-line (436 nm), i-line (365 nm), and KrF excimer lasers (248 nm) in ultraviolet light, while ArF excimer lasers (193 nm) have begun to be used recently.